docs(material/chips): remove unused field visible

Author: jeripeierSBB

src/components-examples/material/chips/chips-input/chips-input-example.ts

@@ -15,7 +15,6 @@ export interface Fruit {
   styleUrls: ['chips-input-example.css'],
 })
 export class ChipsInputExample {
-  visible = true;
   selectable = true;
   removable = true;
   addOnBlur = true;